A process of this type is described in FR-A-2.571.270.
More recently, EP-A-0.362,436 discloses a process in which the permeation is effected in a heated enclosure to limit the condensation, in the membrane module, of condensable components in the gaseous mixture to be separated.
It is known that conventional permeation membranes are very sensitive to traces of impurities carried in the gaseous mixture to be separated, more particularly, in the most frequent case, in which the compressor is of the lubricated type, to traces of lubricating oil, and that the permeation characteristics of the membranes vary considerably with the ambient temperature and that of the gaseous mixture to be separated.